Biostratigraphy, palaeoecology, and palaeobiogeography of the Middle–Late Eocene ostracods, north‐west Fayoum area, Egypt

• Published in: Geological journal (Chichester, England) Vol. 57; no. 9; pp. 3686 - 3705
• Main Authors: El Baz, Sherif M., Wanas, Hamdalla A., Abou Awad, Heba Allah, Assal, Ehab M.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.09.2022; Wiley Subscription Services, Inc
• Subjects: Aquatic crustaceans; Biogeography; Biostratigraphy; Cluster analysis; Egypt; Eocene; Genera; Migrations; Neritic environment; Ostracoda; ostracods; palaeobiogeography; Palaeoecology; Paleoecology; Principal components analysis; Shallow water; Stratigraphy; Egypt
• ISSN: 0072-1050; 1099-1034
• DOI: 10.1002/gj.4496

The present study focuses principally on the late Middle Eocene–early Late Eocene ostracods from two successions (Garet Umm Rigl section and Qasr El Sagha sections), in the northwestern portion of Fayoum area, Egypt. Stratigraphically, the studied successions are classified into three formations (from base to top), the Gehannam, Birket Qarun, and Qasr El Sagha (Temple Member). The recorded ostracod assemblage contains 33 species belonging to 20 genera and 9 families. According to their stratigraphic ranges, three local biozones are recognized, Asymmetricythere yousefi–Loxoconcha pseudopunctatella, Reticulina heluanensis–Leguminocythereis sadeki, and Trachyleberis nodosus nodosulcatus–Ruggeria (Keijella) glabella. The comparison of the proposed biozones with their equivalents inside Egypt denotes a Middle–Late Eocene age for the studied sections. Based on the character of investigated ostracods, three ecozones are distinguished. An inner–outer neritic environment is suggested for the first ecozone, inner‐middle neritic conditions for the second, while shallow water conditions are proposed for the third ecozone. In addition, this paper represents an attempt to detect the palaeobiogeographic provinces of Eocene ostracods by means of multivariate analyses (principle component analysis, Q‐mode cluster analysis and similarity index). These analyses are applied on a matrix composed of some selected Eocene species from 10 regions located at the southern Tethys and western Africa. The results identify three distinctive provinces, North Africa (Algeria, Tunisia, Libya, and Egypt), the Middle East (Jordan and Israel) and West Africa (Senegal, Togo, Ivory Coast and Nigeria). The distinctive affinities between these provinces suggests ostracod migration along the southern Tethys during the Eocene age. This study concentrates on the Middle–Late Eocene ostracods from Fayoum area, Egypt. It represents an attempt to use the multivariate analyses to detect the similarity between the Egyptian ostracods and those from the southern Tethys and western Africa. The results of Principal Compenent Analysis (PCA) and Q‐mode cluster analysis construct three provinces, North Africa, the Middle East, and West Africa. The strong similarity between these provinces supports the migration of ostracods along the southern Tethys during Eocene age.